still



. y w. 1. STILL. PISTON 0F INT'ERNAL COMBUSTION ENGINES. APPLICATION FILED MAY I9. 1919.

1,323,115. K PatentedNov. 25,1919.

2 SHEETS-SHEET I- W. l. STILL.

PlsToN 0F lNERNAL CoMusTloN ENGINES.

APPLICATION FILED MAY I9. 1919.

Patented Nov. 25, 1919.

2 SHEETS--SHEET 2.

WILLIAM JOSEPH STILL,

OF LONDON, ENGLAND.

PISTON OF INTERNAL-COMBUSTION ENGINES.

specification of Letters :Patent Application met May 19, 1919. serial No. 298,203.

To all whom t may concern:

Be it known that I, WILLIAM JosErH STILL, of 7 Princes street, London, S. W. l, England, engineer, have invented certain newf and useful Improvements in Pistons of Internal-Combustion Engines, yof whichA the following is a specication.

This invention relates to improvements in the pistons of internal combustion engines and' has for its object' to provide a piston which can be adequately cooled and which will at the same time stand the strains to which-it is subjected in practice.

The pistons of such engines where the cylinders are' of large bore necessarilyin-A volved large masses of metal and considerable diiculty is experienced in effectively cooling such pistons evenly throughout their mass. Pistons for internal combustion engines have been proposed with integral rings or annular ribs interposed between the piston crown and a supporting bolster on the piston rod so that oil or other cooling liquids can be introduced into the spaces formed between the ribs. In such cases, however, the only arrangement for permitting the circulation of the liquids has consisted in radialholes bored through the ribs so that the cooling fluid entering the central cylindrical chamberypasses the next annular chamber radially through these radial holes and from this rst annular chamber to the next annular chamber and so on in precisel the same manner. By this means the coo ing liquid can find its way from the central chamber to the piston skirt-and ll up the spaces of the piston.

In dealing with pistons of large area the heat absorbed by the pistons is, however, very` great and in fact experience has shown that it amounts in some cases to as much as 40,000 British thermal units per hour per square foot, of surface-which is equivalent to the production of 40 lbs. of steam per square foot of surface per hour. To dissipate this heat, particularly where steam is used as the cooling medium, it is necessary to provide a large area of radiation surface and cause the cooling fluid to flow rapidly in thin streams and in intimate contact over the whole of the radiation surface, and it is the object of my invention to provide a piston where these conditions can be .ful-v filled, and the invention consists broadly'in providing a piston` having ribs or projec-H tions formed between its crown and the piston bolster in such a manner that adequate support will be afforded to the comparatively thin piston crown and thev cooling fluid entering at the center of the piston will lowinthin streams through the passage in close contact with the radiation surface afforded by the ribs or projections to Patented Nov. 2'5, 1919.

an annular space located at the piston crown. In the preferred construction of my invention the grooves or channels through which the cooling liquid Hows intersect.

The invention is capable of considerable modification. in matters of detail and in the accompanying drawings I have illustrated more or less diagrammatically andv by way of example certain constructions and methods by which the invention may be carried out in practice.

In these drawings Figure l is a longitudinal section of apiston on line A-Aof Fig. 2 constructed in accordance with my invention and particularly' designed for use with steam as the cooling uid although itwill be appreciated that water or other cooling uid can be provided for.

Fig. 2 is a partial plan or face view' of the back of the iston with'the supporting bolster remove Fig. 3 is a section on the line B-B 'o Fig. 2..

Fig. 4 is a partial face view of the bolster end of the piston rod showing in particular a 'convenient 'arrangement and -disposition of the holes for accommodating the bolts which secure the piston to the pistonl rod:

Referring to these drawings and particularly to Figs. 1 to 4 the piston l provided with a skirt 2 and the usual packing ring 3 has its crown 4 provided with a system of grooving, the grooves 5 extending in depth from the inner face 6 of the piston-crown to within a short distance of the outer face or wall 7 which, when the piston is in operation, is the combustion side of the. piston. This grooving results yin the productlon of a thin piston crown, and in order to give theI piston as a whole th'e necessary strength, the

plston proper is connected by means of the bolts 8 which pass through bolt holes 8a, to

a bolster 9 on the end of 'the piston rod 10.y

The face 1l of this bolster abuts closely against the outer edges or surfaces of the ribs or projections 12 which are formed as a result of the grooving so that, in eect, the

ybolster supports the thin crown by its engagement with these ribs or projections l2.

The particular form oflgrooving illustrated'l particularly in Fig. 2 consists of series ofy adjoining circular passages, each series following an involute curve extending Jfrom a central recess 13 to the piston skirt 2,and if desirable an annular groove may be provided connecting theserles of grooves at or near the outer periphery of the piston skirt. The circular grooves aforesaid can be cut by means of trepanning tools, and the surfaces, which in practice'are exposed to the cooling iluid, can be increased by screw threading the walls of the groove -by means of a hollow tap, and similarly screw threading the circular projections 12 which are formed as a result of the trepanning operation.

The particular system of groovirg hereinbefore described and as illustrated in Fig. 2 results in the provision of very large heat dissipatin surfaces exposed to the cooling fluid and a so results in'theformation of the supporting ribs or projections 12. Upon v reference to Fig. 2, of the drawings it will be seen that in this particular instance the supporting ribs or projections take two distmct forms one of which, designated 12a may be described asa continuous involute` erates to cool it. IIt will Ibe seen upon reference to Fig. 1 that steam entering yfrom the meet valve of the en 'ne' passes through the ports 15 in Ithe cylin er cover lf3-shown in dottedlines-and thence `passes through the-pasages 17 to the center of the piston crown, and circulates through the grooves or pasages 5 to theperiphery of the piston and 'at the end of the expansion stroke passes to exhausbas will'. be readily understood upon reference to the prior specification above alluded to.

'Pistons of the foregoing general character will befound capable of effective cooling by steam. Moreover such pistons will be very strong structurally by reason of the support y'nazaire they pass through thef piston crown may be 'of asection corresponding to the section of metal left between certain of the grooves whether that section be circular as in Fig. 2 or of other form.A

While I herein show and describe one form of my invention, I would have it understood that changes may be made in the form, proportion and construction of the several parts, without departin from the spirit of my invention, and within the scope of the appended claims.

In cases where steam is not used at the back of the piston or where cooling is desirable any suitable known means may .be adopted for circulating the cooling fluid. For instance, the ywater or other cooling fluid' may be passed in through the piston ro and out through a trombone. or sliding joint as will be readily understood.

What I claim and desire to secure by Letters Patent is v 1. In an internal combustion engine, a plston rod having a bolster 'at its outer end, said bolster having a centrally .arranged recess in its outer side and passages,v leading to said recess, and a piston having its crown provided, on the inner side, with a central recess and with ribs and passages between said ribs, said passages communicating with said recess; the said bolster of the piston rod abutting a ainst and being secured to the crown of t e piston.

2. In an internal combustion engine, a piston rod having a bolster at its outer end, said bolster having a centrally arranged recess in its outer side and passages leading to said recess, and a piston having its crown provided on the inner side with a central recess, and with ribs and passagesbetween said ribs' and communicating with said recess, the crown being further provided with an annularpassage with which the first named passages communicate at their outer n ends; the said bolster of the piston rod abutting against and being secured to the crown of the iston.

In witnesswhereof I WILLIAM JOSEPH STILL.

aiiix my signature. 

